The present invention relates to a unified assembly for control of fluid flow in a liquid dispensing system and to a liquid dispensing system which includes such an assembly. In the dispensing of liquids on demand from an exhaustible source, such as a cask, keg, barrel or other container in the case of beverages, where the liquid is often pumped through lengthy piping to a dispensing tap, there is a problem that as the container empties, air (or other gas as may be used in the dispensing) can be drawn into the piping so that eventually merely bubbles, froth or foam of the liquid are dispensed. When the empty container is recharged with liquid, or replaced by a full container, it is usually necessary to purge the whole length of piping from the container to the dispensing tap of foam before liquid can again be dispensed; this it will be appreciated is both time consuming and inconvenient. Examples of typical beverage dispensing systems in which a considerable length of piping through which beer is supplied from a cask by way of an electrically driven pump to a counter-mounted dispensing tap and in which the aforegoing disadvantages may occur if the cask empties during a dispensing operation are disclosed in our British Patent Specification Nos. 2,172,265A and 2,172,266A.
It is an object of the present invention to provide an assembly for control of fluid flow in a liquid dispensing system of the kind discussed above by which the disadvantages referred to may be alleviated and which assembly may be of a compact unified structure, be reliable, be manufactured in quantity at relatively low cost and be readily installed in existing liquid dispensing systems of the kind referred to. Although the present invention was primarily developed for use in dispensing systems for beverages such as beer, stout, lager, cider and so-called soft drinks which are themselves or have liquid ingredients which are supplied by fluid pressurising means such as a pump from an exhaustible container, it will be realised that the invention may readily be applied to liquid dispensing systems other than for beverages.